Puma board for FreeEMS

[Fred]

Spin2 should be there just to fix up little problems that you found with Spin1. Eg this foot print was wrong, this track should have been cut etc. The way Spin 2 is moving is a completely different board. Done right Spin2 could be a completed product. What I see is Spin2 changed so much that it is a different product.

Exactly.

I have ever intention to use my Spin1 board for many years to come. It has all the functionality that I require. Sure it has a few problems, but nothing that a semi skilled person can't handle.

True.

I'm not a big fan of using the latests and greatest chips from a single supplier. Eg Don't use a fancy switching regulator made by one company, when a generic one will do, that can be sourced from many suppliers.

BIG plus one. They'll not be the first designers to be f***ed by EOLing of chips.

The only reason that I should need to change to Spin2 will be if Fred decides that the code won't support it any more. (Which I doubt he would do).

The only changes that you'll MAYBE have to make are about always on power, and if I possibly can, I will make that optional. I haven't thought about it in enough detail to say at this stage. In any case, you should be able to hack a spin 1 into a usable form with a mess of jumpers and extra components no matter what happens.

Jared, heat reduction is a bullshit thing to be doing as is, there is very little heat from the board and regs right now, and under a fully configured app it still wouldn't be much worse. Plus, putting heat out of the board into a sink is the best option BY FAR, and we're dodging that from vibration resistance paranoia and compliance with standards that none of US (performance car enthusiasts) care about, when hundreds of OEMs use to220 stuff reliably on production vehicles that last for decades and hundreds of thousands of kilometers.

What is true, is that the power supply architecture needed a rework, but moving to some specific switcher seems daft when cheap common linear regs will work admirably for all intents and purposes.

Fred.

[Spudmn]

I have found a couple of mistakes in the BOM

The Digi-Key Part Number don't match the values listed
399-1151-1-ND is not 3.3nf
311-1123-1-ND is not 330pf

[jharvey]

Spudman, thanks for the report/verification. Sorry for the mistake.

I'm looking to change the 3.3nF to 445-1333-1-ND and the 330pF to 478-1365-6-ND, however, I understand Marco's ordered against that BOM, so I wonder what's on the built boards. I believe in-circuit testing will be inclusive, as the resistors and other components will make the meter read incorrectly. Not sure if we can use SPICE to figure out what we should measure when assembled.

[Spudmn]

As I suspect that it is the PLL that is giving me all the problems can some one please confirm what values work before I order the parts.

Fred do you know the values that you are using in your PLL?

[Fred]

No, but Marcos does, one moment, I will direct him here.

[nitrousnrg]

Sorry for the late reply, I didn't check the forum for a couple of days.

The BOM used to say 220pF, and all my boards had 220pF and 3.3nF caps, with a 3.3k resistor. The schematic says 330pF and 3.3nF, with a 3.9k resistor, and those are the values used in the TA card.

So, both combinations work. The BOM was changed a week ago, replacing the 220pF by 330pF, just to respect the schematic.

I recall your values were slightly off, but not that far from these. If you don't have close values in SMT, try what I did for my first board:

http://nitrousnrg.imgur.com/puma#VVpNm

When I had problems I checked the VCO input voltage on the PLL resitor. If it was totally pulled up (2.5v), then something was wrong (frequently, a crystal with a non-soldered lead). As you know, ~1.5v means something is oscillating in there (well, now I know you have 1.5v and yours doesn't work).

[Spudmn]

Thanks

I ordered 330pF and 3.3nF and a new Xtal today. I will replace every thing in the PLL and see how I get on.

[nitrousnrg]

Good, let me know how it turns out. I guess you have a solder station, I never removed one of those crystals... it seems tricky.

[KW1252]

Just a quick remark from my build thread; be sure to include fiducials in Spin2! It's an absolute must if you ever want to use a pick-and-place machine to assemble the board

[nitrousnrg]

Just a quick remark from my build thread; be sure to include fiducials in Spin2! It's an absolute must if you ever want to use a pick-and-place machine to assemble the board

Yeah, that won't be forgotten :-)

An interesting and expensive IC I found
http://datasheets.maxim-ic.com/en/ds/MAX6675.pdf

Pros: Thermocouple driver, 0°C to 1024C, 3v to 5.5v supply, and a digital SPI output.
Cons: $14 in qty 1, Temp range -20 to 85°C (but junction max temp is 150°, so it will work at higher temps with screwed readings, which is acceptable, IMO)

After I solve the components acquisition I'm laying out the SMPS and P&H. I'm going to print a $5 board here, since the power supply doesn't have any fine pitch components and will work just ok for testing.